1. Field of the Invention
This invention relates to an electrical circuit for generating a defined digital signal in response to a change in the load in a remote sensing circuit and has application, for example, in mass transit vehicles that have passenger presence sensing circuits associated with vehicle doors. The electrical circuit generates a defined digital input to the vehicle control computer.
2. Description of Related Art
This application relates to sensing of the presence of passengers at the doors of mass transit vehicles. The prior art is described in our co-pending application Ser. No. 11/084,789 entitled “Capacitance Activated Switch Device” incorporated herein by reference. As explained therein, it is common for vehicle operators to be able to place certain doors in a condition enabling passengers to open such doors by contacting a switch mounted on the side of the door, such as a mechanically-operated touch bar. In our co-pending application, we describe a capacitance-activated switch device attached to the door that senses the presence of a passenger entering an alternating electric field. Electrical conduits supply power to the switch. The electrical conduits are used to signal the presence of a passenger at the door. The conduits are fed through a limited space along the hinged edge of the door. Space is also limited for circuitry attached to the door itself. It is an advantage, according to this invention, to address these space limitations by using the two-wire power leads to the door mounted or remote sensor circuit to signal the passenger presence at the door.